Radiation-sensitive silver halide emulsions containing amine boranes and gold compounds

ABSTRACT

In direct positive emulsions chemically fogged with amine boranes, the tendency for red light to bleach the image because of red light sensitivity is reduced by digesting the molten emulsion in the presence of a water-soluble gold compound. The gold compound is added in an amount from 0.400 X 10 5 to 3.40 X 10 5 moles of Au or Au per 1.5 moles of silver nitrate. The gold compound may be added before or after the addition of the amine borane fogging agent.

United States Patent Inventor Appl. No. Filed Patented AssigneeRADIATION-SENSITIVE SILVER HALIDE EMULSIONS CONTAINING AMINE BORANES ANDGOLD COMPOUNDS 1] Claims, No Drawings US. Cl 96/101,

96/64 Int. Cl G03c 1/36 Field of Search 96/101, 64

[5 6] References Cited UNITED STATES PATENTS 3,361,564 1/1968 Bigelow etal. 96/101 FOREIGN PATENTS 723,019 2/195 3 Great Britain 96/64 PrimaryExaminer -Norman G. Torchin Assistant ExaminerR. E. FichterAttorney-Lynn Barratt Morris ABSTRACT: In direct positive emulsionschemically fogged with amine boranes, the tendency for red light tobleach the image because of red light sensitivity is reduced bydigesting the molten emulsion in the presence of a water-soluble goldcompound. The gold compound is :added in an amount from 01400 10 to3.40X10 moles of Au or Au per 1.5 moles of silver nitrate. The goldcompound may be added before or after the addition of the amine boranefogging agent.

RADIATION-SENSITIVE SILVER HALIDE EMULSIONS CONTAINING AMINE BORANES ANDGOLD COMPOUNDS BACKGROUND OF THE INVENTION 1. Field of the InventionThis invention relates to radiation sensitive direct-positivephotographic elements. This invention also relates to radiationsensitive direct-positive silver halide emulsions for said elements.More particularly, this invention is directed to directpositive silverhalide emulsions having reduced red light sensitivity and lowsusceptibility to the Herschel effect.

2. Description of the Prior Art Direct-positive elements are, of course,known and they may be imaged in a variety of ways. For example, a silverhalide emulsion may be given a short overall exposure of high intensityradiation and then given a longer imagewise exposure to radiation oflower intensity. Upon development, a directpositive image will beobtained. Another method is to expose imagewise and develop and thenflash expose and redevelop. A still further method is to chemically fogthe silver halide grains with, for example, formaldehyde, hydrazine,sodium arsenite, silver ions and other nonsulfide fogging agents,instead of using a solarizing exposure. Upon imagewise exposure anddevelopment of such a chemically fogged element, a positive image isobtained. In direct-positive photographic elements utilizing this lattermethod, there is usually incorporated a desensitizing compound, usuallya colored desensitizing dye. A new direct-positive emulsion which is animprovement over the above type uses alkyl amine boranes as the foggingagents. This is disclosed and claimed in Bigelow and Burt, U.S. Pat. No.3,361,564. This newer product gives images of high reversal density andhigh speed. This product does not require the use of a coloreddesensitizing dye and therefore the directpositive images are free ofstain which was one of the disadvantages of the prior artdirect-positive elements. The use of alkyl amine boranes in silverhalide emulsions eliminates the need for more than one exposure andeliminates the need to use formaldehyde as the fogging agent.Formaldehyde not only acts as a fogging agent but has a strong effect onthe hardness of the colloid carrier. Although the use of alkyl amineboranes as fogging agents in direct-positive emulsions has manyadvantages over the prior art, it suffers from the disadvantage of beingoverly sensitive in the red region of the spectrum and easily bleachesupon multiple exposure through popular orange and ruby masking materialsbecause ofthis red light sensitivity.

SUMMARY OF THE INVENTION This invention relates to direct-positiveemulsions and to their preparation by incorporating an amine boranecompound in fogging amounts with a silver halide emulsion; andat somepoint prior to the end of digestion, adding from 0.400Xl to 3,400Xl0mole of Au or Au per 1.5 mole of silver halide of a soluble goldcompound, e.g., auric chloride and aurous thiocyanate. The emulsionpreferablyis a gelatinosilver chlorobromide emulsion containing fromabout 80 to 90 percent by weight of silver bromide, the rest beingsilver chloride and optionally the system may contain, in addition tothe two halides, from 0 to 6 percent by weight of silver iodide. Theborane fogging agents may be added to the emulsion in amounts rangingfrom 0.0005 gram to 18.0 grams per 1.5 moles of silver halide andpreferably from 0.20 to 2.00 grams per 1.5 moles of silver halide. Theymay be added either as a solid or dissolved in a suitable solvent. Theeffectiveness of the borane compounds in fogging a silver halideemulsion is influenced by the pH of the system, the higher the pH, thegreater the fogging for a given amount of borane compound. Of course,certain of the borane compounds are more effective than others when usedin equivalent quantities. The fogging amounts of a particular amineborane within the above limits can easily be determined empirically. Thefogging effect produced by the borane compounds is bleachable by lightexposure prior to development including the red region of the spectrum.A suitable developer may be any conventional alkaline photographicdeveloping solution which would be used for standard processing of theabove direct-positive emulsions in the absence of the amine boranecompounds. Among the amine borane compounds which have been found usefulare those disclosed in Bigelow and Burt, U.S. Pat. No. 3,361,564 andBurt, U.S. Ser. No. 472,313 filed July 16, 1965, U.S. Pat. No.3,445,235, May 20, 1969. For most efficient fogging action it ispreferred that the amine borane corripounds be added to the silverhalide emulsion after it-has beeh made, ripened, and washed to removethe excess salts resulting from the precipitation of the silver halides.Conveniently, the borane compounds are added just prior to or during thedigestion or after ripening period. The pH of the emulsion is adjustedto between 5 and 9 and maintained at this level during digestion. It isat this point that the soluble gold salt is added either before, duringor after the addition of the amine borane compound. As shown in exampleII, the gold salt can be added after the digestion step.

In addition to auric chloride and aurous thiocyanate mentioned above,other soluble gold salts may be used, e.g., sodium chloroaurate,potassium aurate, potassium chloroaurate, potassium bromaurite,potassium iodoaurite, potassium iodoaurate, potassium auricyanide andpotassium aurithiocyanate. While the silver halide system used in thisinvention is generally of the silver chlorobromide type other types maybe used such as silver chloride, silver iodobromide and silveriodochloride.

DESCRIPTION OF THE PREFERRED EMBODIMENT While a minimum of 0.400 l0 per1.5 moles of silver nitrate and a maximum of 3.40 10 mole of gold (Au"or Au") show good results the preferred range is from 0.800X l0 to 3.0010 per 1.5 moles of silver nitrate.

To test the effect of digesting the amine borane fogged emulsions in thepresence of a soluble gold salt, the coated layers weresensitometrically tested using 3200 K. quartz iodine illumination.Generally the speeds and maximum densities of the samples in the examplebelow were comparable. Typical IOO/E speeds at a density of 0.25 are2800 10 with 4.50 maximum densities and 0.0l0.04 minimum densities. Thecoated elements were also exposed to the quartz iodine illumination of960 foot-candles for 3 minutes through a Wratten 025 (Red) filter(manufactured by the Eastman Kodak Company), developed, fixed, washed,dried and read with a densitometer. The densities obtained areproportional to the resistance of the emulsion to bleaching when exposedto red light.

The invention will now be illustrated by the following example.

EXAMPLE 1] To acidified aqueous solutions of gelatin each containing 1.5moles of potassium chloride and 18 milligrams of rhodium chloride (RhCl'3H O) there were rapidly added solutions containing 1.5 moles of silvernitrate. To each of the resulting mixtures there was added an aqueoussolution containing 0.4 mole of potassium bromide. The emulsions wereripened by heating for 10 minutes at 160 F. A second aqueous solutioncontaining 0.6 mole of potassium bromide was added to each of theemulsions which were then ripened for 10 minutes at 160 F.

The resulting emulsions were then coagulated, washed and redispersed inthe manner disclosed in Moede, U.S. Pat. No. 2,772,165 issued Nov. 27,1956. The temperature of the redispersed emulsion was raised to F. andthere was then added to each 87 grams of gelatin, and the pH wasadjusted to 5.7 with NaOH. Morpholine borane and trimethylamine boranewere then added as indicated in the following table and the emulsionswere digested at 130 F. for 40 minutes. During this period, gold saltswere added in the amounts indicated in said table. The usual coatingaids including a gelatin hardener were then added and the emulsions wereeach coated on a polyethylene terephthalate film support having ananchoring polymer substratum and dried in the conventional manner.Sample strips of the coated films were exposed as described above anddeveloped for lriminutes at 60 F. in a developer having the composition:

Water 750.0 ml.

N-methyl-p-aminophenol hydrogen sulfate 1.5 grams Sodium Sulfite(anhydrous) l9.5 grams Hydroquinone 6.0 grams Sodium Carbonate(anhydrous) 24.0 grams Potassium Bromide 0.8 grams Water to make 1.0liter The strips were then immersed in a conventional short stop for 5to. 10 seconds and then fixed for 3 minutes in a conventional fixer, andthen washed and dried. Evaluation of the resulting samples gave thefollowing results.

Density Mole Au or Au+ per after Sample 1.5 moles Gold Amine boranefogging exposure 0. AgNO compd agent to red light 1 None 3.8 mg./1.5moles 1.35

AgNO: morpholine borane. 2 .418X10 2.47 3- .837X- 3.20 4 1. 67BX10 4.50+ 5 3. 350X10' 4. 50+ 6 6. 700x10 4. 50+ 7 13. 400x10 AuCl:. -..d0 4.50+ 8 1. 254X10' AuCla.. 160 mg./l.5 moles 4. 50+

AgNO of trimcthyl amine borane. 9 2. 746X10' AuC13. 3.8 mg./1.5 moles 4.50+

AgNOa tertiary butylamine borane. 10 1. 675Xl0- AuONS... 3.8 mg./1.5moles 4. 50+

AgNO: morpholine borane.

Increasing density values indicate increasing resistance to red lightbleaching 1,000 watt quartz iodine lamp with Wratten 025 filter). Atlevels of gold compound (Samples 5, 6 and 7) above 3.350 10 mole Authere is no improvement in resistance to red light bleaching.

EXAMPLE II An emulsion was made as described in example I and 3.8milligrams of morpholine borane per 1.5 moles of silver nitrate wasadded as the fogging agent. After the digestion step, the gold salt,auric chloride, was added in the quantities indicated in the tablebelow. There were then added as one of the final additions, 200milligrams per 1.5 moles of silver nitrate of the optical sensitizingdye, 3carboxymethyl-5[(3- ethyl-2(3)-thiazolinylidene)ethylidene1-rhodanine. This increased the speed of the coated elementabout 4-fold over that of an element not containing the dye. Theresulting emulsion was coated, dried, exposed and processed as describedin example l to give the following results:

Density after exposure to red light 3 minutes, 960

Sample Mole Au fool-candles filtcrcd No. 1.5 moles AgNo, with Wrattcn025 filter l 0 0.37 2 0.837Xl0' 0.87 J l.675 l0" 4.00 4 3.350Xl0' 4.50

Increasing density values indicate increasing resistance to red lightbleaching.

Other sensitizing dyes, e.g., carbocyanine and merocyanine dyes,including those described in U.S. Pat. No. 2,493,748, Jan. 10, 1950, canbe used in the emulsion of this invention.

From emulsion-coated elements of the above example, good duplicates canbe made by contact-printing, using either carbon arc lamps or tungstenphotofloods as a light source. The emulsion-coated elements may be usedfor reproducing continuous tone negatives, halftones, line copy,engineering drawings, etc. The direct-positive elements of thisinvention may also find use in color photography.

The photographic elements of this invention provide direct positiveshaving extremely low minimum densities and high maximum densities andare fast but at the same time show a high resistance to bleaching due tored light sensitivity. As indicated above, the elements of thisinvention may be developed in any conventional developing solution usingstandard techniques. Variations in the developer composition will havemuch the same effect asit would have in developing conventionalnonreversal emulsions. No preexposure operations or auxiliary processingprocedures are necessary or desirable in using the novel elements ofthis invention. It is also unnecessary to utilize stain producingdesensitizing dyes or other desensitizing compounds in the emulsions.The amine boranes as chemical fogging agents are far superior toformaldehyde, the well known and conventional fogging agent of the priorart, because the amine borane compounds do not have any hardening effecton the gelatin layer. The amine boranes have one small disadvantage andthat is desensitization by kinking but this is easily overcome by theaddition of a group Vlll metal salt, e.g., rhodium chloride as disclosedand claimed in Burt, U.S. Ser. No. 472,313 filed July 15, 1965.

In place of gelatin, other material or synthetic water-permeable organiccolloid binding agents can be used. Such agents include water-permeableor water-soluble polyvinyl alcohol and its derivatives, e.g., partiallyhydrolyzed polyvinyl acetates, polyvinyl ethers, and acetals containinga large number of extralinear -Ch CHOH- groups, hydrolyzed interpolymersof vinyl acetate and unsaturated addition polymerizable compounds suchas maleic anhydride, acrylic and methacrylic acid ethyl esters andstyrene. Suitable colloids of the last-mentioned type are disclosed inU.S. Pat. Nos. 2,276,322; 2,276,323; and 2,397,866. The useful polyvinylacetals include polyvinyl butyraldehyde acetal and polyvinyl sodiumo-sulfobenzaldehyde acetal. Other useful colloid binding agents includepoly-N-vinyllactams of Bolton, US. Pat. No. 2,495,918, the hydrophiliccopolymers of N-acrylamide alkyl betaines described in Shacklett, U.S.Pat. No. 2,833,050 and hydrophilic cellulose ethers and esters.

The emulsions of this invention may be coated on any suitable supportincluding paper and transparent film supports. For example, thecellulose supports, e.g., cellulose acetate, cellulose triacetate,cellulose mixed esters, etc., may be used. Polymerized vinyl compounds,e.g., copolymerized vinyl acetate and vinyl chloride, polystyrene, andpolymerized acrylates may also be mentioned. The film formed from thepolyesters made according to theteachings of Alles, U.S. Pat. No.2,779,684 and the patents referred to in the specification of thatpatent. Other suitable supports are the polyethyleneterephthalate/isophthalates of British Pat. No. 766,290 and CanadianPat. No. 562,672 and those obtainable by condensing terephthalic acidand dimethyl terephthalate with propylene glycol, diethylene glycol,tetramethylene glycol or cyclohexane-l,4-dimethanol (hexahydro-p-xylenealcohol). The films of Bauer et al., U.S. Pat. No. 3,052,543 may also beused. The above polyester films are particularly suitable because oftheir dimensional stability. The emulsions are generally coated on thesupports in quantities to give a coating weight of about 50-75milligrams of silver halide per square decimeter of support surfacearea.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

I BrNIBH;

wherein R, is an alkyl radical of l to about carbon atoms, and R and Rare each taken from the group consisting of H and alkyl radicals of l toabout 20 carbon atoms.

4. An emulsion according to claim 1 wherein the amine borane istrimethylamine borane.

5. An emulsion according to claim 1 wherein the amine borane istertiarybutylamine borane.

6. An emulsion according to claim 1 wherein the amine borane is aheterocyclic amine borane.

7. An emulsion according to claim 1 wherein said amine borane ismorpholine borane.

8. An emulsion according to claim ll wherein said silver halide issilver chlorobromide containing -90 percent silver bromide.

9. An emulsion according to claim 1 containing an optical sensitizingdye.

10. A process which comprises admixing with a liquifiedradiation-sensitive silver halide emulsion prior to completion ofdigestion, fogging amounts of at least one amine borane compound andprior or subsequent to completion of digestion at least onewater-soluble gold compound in an amount sufficient to provide 0.400 l0"to 3.40Xl0 mole of Au"" or Au per 1.5 moles ofsilver halide.

111. A process according to claim 10 wherein the emulsion is a gelatincontaining emulsion and the gold compound is auric chloride.

W105) UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2Dated September 21, 1971 Cortland R. Burt Inventor(s) It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

In the ABSTRACT, line 6, "0.L 2: 10 to 3A0 x 10 should be --0.L 00 x 10"to 3.1;0 x

Column 1, line 55, "0.1400 x 10 to ,11,00 x 10 should be --0.u0o x 10-5to 3.14002: 10- Column 2, line 3, "0.u00 X. 10 should be --0.L;00 x 10-line 31;, "3.1 0 x 10 should be --3.).IO x 10- lines and 36, "0.800 x 10to 3.00 x 10 should be --0.800 x 10- to 3.00 x 10' line be, "2800 x 10-should be --2800 x 10- Column 3, line "3-35 X 1 should be --3.350 x 10-line 7 37 X 1015" should be --O.837 1: 10' i e 73, "1.675 X 1015" shouldbe --l.675 x 10'5";

line 7 4, "3-35 X 1015" should be --3.350 x 10' C l 5, line )4, -M 1should be --0.h00 x 10- Column 6, line 15, "0.)400 x 10 to 3.140 x 10should be --0.L o0 x 10' to .h0 x 10- Signed and sealed this 16th day ofMay 1972.

(SEAL) Ittest:

EDWARD M.FLEICHER,JR. ROBERT GOTTSCHALK Lttesting Officer Co issioner ofPatents

2. An emulsion according to claim 1 wherein the binding agent for thesilver halide embodies gelatin.
 3. An emulsion according to claim 1wherein the amine borane is an alkyl amine borane of the formula:
 4. Anemulsion according to claim 1 wherein the amine borane is trimethylamineborane.
 5. An emulsion according to claim 1 wherein the amine borane istertiarybutylamine borane.
 6. An emulsion according to claim 1 whereinthe amine borane is a heterocyclic amine borane.
 7. An emulsionaccording to claim 1 wherein said amine borane is morpholine borane. 8.An emulsion according to claim 1 wherein said silver halide is silverchlorobromide containing 80-90 percent silver bromide.
 9. An emulsionaccording to claim 1 containing an optical sensitizing dye.
 10. Aprocess which comprises admixing with a liquified radiation-sensitivesilver halide emulsion prior to completion of digestion, fogging amountsof at least one amine borane compound and prior or subsequent tocompletion of digestion at least one water-soluble gold compound in anamount sufficient to provide 0.400 X 10 5 to 3.40 X 10 5 mole of Au orAu per 1.5 moles of silver halide.
 11. A process according to claim 10wherein the emulsion is a gelatin containing emulsion and the goldcompound is auric chloride.